When doctors won't tell . . .
Of all the online nutritional information, nutritional facts, medical and
dietary sites there are to choose from, in an article entitled "How
to ease the pain" The Sunday Times magazine,
Culture, published a list of just five websites it
considered reliable and informative.This site was one of that five.

CONDITIONS
AND DISEASES PREVENTED AND HELPED BY A LOW-CARB, HIGH-FAT DIET

"NH&WL may be the best non-technical book on diet ever
written"
Joel Kauffman, PhD, Professor Emeritus, University of the Sciences,
Philadelphia, PA

Fats Explained

Explanation of terms

Fat
is a substance which contains one or more fatty acids and is the principal
form in which
the body stores energy. It is also used as an insulating material both just
beneath the skin and
around some of the internal organs. Fat is essential in the diet to supply an
adequate amount of
essential fatty acids and for the absorption of the fat-soluble vitamins: A, D,
E and K.

The chemical and physical properties of a fat are determined by the relative
amounts of the
various fatty acids of which it is composed. Generally, the more saturated the
fatty acid content,
the harder the fat will be at room temperature; the more unsaturated its
content, the runnier it
will be. All fats are a mixture of different fatty acids.

Fatty Acids

All fats are composed of fatty acids, of which there are dozens in nature. A
fatty acid is an organic acid having a chain of carbon atoms coupled to
hydrogen atoms at the
side and a carboxyl radicle at one end. The carbon atoms are joined together
with mainly a
single bond plus a number of 'double bonds'. It is the difference between these
that
differentiates the various fatty acids.

Saturated fatty acids
have no double bonds and this makes them stable.

The diagram above is of
Stearic acid
. It has 18 carbon atoms and no double bonds. It is
designated
18:0
. Because all the carbon atoms are surrounded by hydrogen atoms, it is called
saturated
. As the hydrogen atoms are all close together, it is difficult to bend. It is
this resistance
to bending that makes most saturated fats solid at room temperature.

Unsaturated
fatty acids
are those where two or more of their carbon atoms are connected with 'double
bonds'.

Here we have another 18 carbon fatty acid:
Oleic acid
, the major fatty acid in olive oil. This has
one '
double bond
' in the middle. Fatty acids with one double bond are called
mono
-unsaturated.
It is designated by the term
18:1
. Because of the double bond this fatty acid can bend and is
liquid at room temperature. Oleic acid is also the most abundant fatty acid in
animal fats and in
human fat.

Poly-
unsaturated fatty acids
are those with two or more double bonds.

The one above is
Linoleic acid
, the most abundant fatty acid in vegetable seed oils such as sunflower,
safflower,
soya and corn oils. This has two double bonds, the first after the sixth carbon
atom. This makes
it an
Omega-6
fatty acid. If the first double bond follows the third carbon atom, the fatty
acid
is an
Omega-3
fatty acid. The shorthand for linoleic acid is
18:2.

Some fatty acids come in two configurations: Omega-3 and Omega-6.
Linolenic acid
, an 18-carbon molecule with three double bonds, is an example.
Alpha-linolenic acid
is
Omega-3
,
while
Gamma-linolenic acid
is
Omega-6
.

All polyunsaturated fatty acids are liquid at room temperature.

The unsaturated fatty acids are not stable; they react gradually with oxygen in
the air and
become rancid. This oxygenation process produces molecules known as
free radicals
which are
known to have undesirable effects on the body. The more unsaturated a fatty
acid is, the more
liable it is to oxidation. This is why polyunsaturated margarines must be kept
refrigerated.

Cis and trans bonds

Generally, in Nature, fatty acids' double bonds are as shown above with the
single hydrogen
atoms at a double bond on the same side of the molecule. This is called a
cis
configuration.
However, in the process of margarine manufacture, liquid oils are not much
good. They have to
be made more solid. The process which does this is called
hydrogenation
. During hydrogenation,
some of the double bonds are twisted so that the hydrogen atoms lie on opposite
sides, as in the
diagram below. This configuration is called
trans.

(In the diagram of linoleic acid above, both double bonds are shown as
trans
bonds.)

Fats are attacked by oxygen. Just like iron left out in the rain, fats oxydise
(rust). But oxygen can only attack fats where there are double bonds. This is
why saturated fats don't spoil but polyunsaturated margarines must be kept in
the fridge. And the more double bonds a fatty acid has, the more it oxydises
and the more '
free radicals
' it throws off.

Fats and fatty acids

All fats contain a mixture of different fatty acids, both saturated and
unsaturated. The fatty
acid content of some typical foods are tabled below. The total percentages are
less than 100%
because of the glycerol and other compounds that are present.
Note that, although animal fats
are generally thought of as being saturated fats, most are less than fifty
percent saturated.

Table :
Fatty acid content of typical foods

Percentage of fat

% Fat

Sat

Mono

Poly

Milk cow's

3.9

64

28

3

human

4.1

50

39

9

Cheese,
Cheddar

33.5

63

27

4

Eggs

10.9

31

39

11

Beef

27.4

41

47

4

Pork

25.5

35

42

15

Chicken

12.8

30

45

20

Liver,
lamb's

6.2

28

29

15

Mackerel

22.9

20

49

20

Butter

76.9

50

34

3

Lard

95.5

39

45

11

Margarine
hard

81.0

39

47

10

polyunsaturated

81.0

17

27

52

Blended
cooking oil

99.9

13

25

58

Peanuts,
roasted

49.0

12

38

37

Chocolate,
milk

30.3

58

33

4

Last updated 24 March 2001

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Disclaimer: Second Opinions is the website of Barry Groves PhD, offering online nutritional facts and online nutritional information. This website should be used to support rather than replace medical advice advocated by physicians.sitemap